1. Field of the Invention
The present invention relates to circuit boards having predetermined circuit patterns formed thereon, electronic apparatuses utilizing the circuit boards, and methods for manufacturing the circuit boards.
2. Description of the Related Art
Generally, a process of designing a circuit board includes a sequence of designing the circuit(s) to be formed on the circuit board, manufacturing the circuit board according to the determined design values, and then testing the manufactured circuit board. When a problem is found during testing, the design of the circuit(s) may be modified and, thereafter, the modified circuit board is manufactured and tested. This sequence of designing, manufacturing and testing is repeated until a circuit board meeting desired or required operational specifications is formed.
To make testing of circuit boards easier, circuits having low resistance elements (inspection points) formed thereon have been designed. At various stages of testing, repairing, development and/or production, pre-determined portions of the circuit can be intentionally short-circuited through the low resistance elements, or the low resistance elements can be removed to detect the current flowing through one or more components on the circuit board. Since the low resistance elements are not necessary for the final intended functionality of the circuit board, it is desirable that all of the low resistance elements are replaced by conductive patterns (interconnections) at the time of mass-production of circuit boards. However, since the utilization of the low resistance elements can make inspection of defective circuit boards simpler and easier, circuit boards having the low resistance elements mounted thereon are often mass-produced.
For example, Japanese Unexamined Patent Application Publication No. 07-86729 and Japanese Unexamined Utility Model Registration Application Publication No. 62-4165 disclose techniques for mounting an inspection point on a circuit board.
When low resistance elements are not formed on the circuit board, an inspection of the circuit board requires removing mounted electronic components one by one to confirm proper operation of each electronic component. In addition to being very time and labor intensive, another disadvantage of this approach is that the mounted electronic components may be broken at the time of removal. Japanese Unexamined Patent Application Publication No. 2003-168501 discloses a technique for overcoming such a disadvantage.
Mounting of low resistance elements on mass-produced circuit boards advantageously makes the inspection easier. However, the high costs for both resistance elements and for mounting them undesirably result in an increase in overall cost of a circuit board. In addition, since defects occur as result of mounting the low resistance elements at the same probability as that of mounting ordinary resistance elements, the production yield of circuit boards undesirably decreases in proportion to the number of the mounted resistance elements.
Thus, there is a need to provide circuit boards that more easily allow for inspections to be performed while lowering manufacturing and testing costs and improving production yields. Furthermore, there is a need for an improved method of manufacturing and testing such circuit boards.